Detection of SARS-CoV-2 in Air and on Surfaces in Rooms of Infected Nursing Home Residents

  1. Kimberly J Linde
  2. Inge M Wouters
  3. Jan A J W Kluytmans
  4. Marjolein F Q Kluytmans-van den Bergh
  5. Suzan D Pas
  6. Corine H GeurtsvanKessel
  7. Marion P G Koopmans
  8. Melanie Meier
  9. Patrick Meijer
  10. Ceder R Raben
  11. Jack Spithoven
  12. Monique H G Tersteeg-Zijderveld
  13. Dick J J Heederik
  14. Wietske Dohmen
  15. COCON Consortium

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Abstract

There is an ongoing debate on airborne transmission of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) as a risk factor for infection. In this study, the level of SARS-CoV-2 in air and on surfaces of SARS-CoV-2 infected nursing home residents was assessed to gain insight in potential transmission routes. During outbreaks, air samples were collected using three different active and one passive air sampling technique in rooms of infected patients. Oropharyngeal swabs (OPS) of the residents and dry surface swabs were collected. Additionally, longitudinal passive air samples were collected during a period of 4 months in common areas of the wards. Presence of SARS-CoV-2 RNA was determined using RT-qPCR, targeting the RdRp- and E-genes. OPS, samples of two active air samplers and surface swabs with Ct-value ≤35 were tested for the presence of infectious virus by cell culture. In total, 360 air and 319 surface samples from patient rooms and common areas were collected. In rooms of 10 residents with detected SARS-CoV-2 RNA in OPS, SARS-CoV-2 RNA was detected in 93 of 184 collected environmental samples (50.5%) (lowest Ct 29.5), substantially more than in the rooms of residents with negative OPS on the day of environmental sampling (n = 2) (3.6%). SARS-CoV-2 RNA was most frequently present in the larger particle size fractions [>4 μm 60% (6/10); 1–4 μm 50% (5/10); <1 μm 20% (2/10)] (Fischer exact test P = 0.076). The highest proportion of RNA-positive air samples on room level was found with a filtration-based sampler 80% (8/10) and the cyclone-based sampler 70% (7/10), and impingement-based sampler 50% (5/10). SARS-CoV-2 RNA was detected in 10 out of 12 (83%) passive air samples in patient rooms. Both high-touch and low-touch surfaces contained SARS-CoV-2 genome in rooms of residents with positive OPS [high 38% (21/55); low 50% (22/44)]. In one active air sample, infectious virus in vitro was detected. In conclusion, SARS-CoV-2 is frequently detected in air and on surfaces in the immediate surroundings of room-isolated COVID-19 patients, providing evidence of environmental contamination. The environmental contamination of SARS-CoV-2 and infectious aerosols confirm the potential for transmission via air up to several meters.

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  1. Version published to 10.1093/annweh/wxac056
  2. ScreenIT

    SciScore for 10.1101/2022.02.16.22271053: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    EthicsIRB: No medical ethical approval was needed for this study as evaluated by the Medical Research Ethics Committee of University Medical Centre Utrecht; a declaration of non-compliance with the scope of the Dutch Medical Research Involving Human Subject Act was obtained.
    Consent: Oral informed consent was obtained from patients and/or from an authorised legal representative or family member.
    Field Sample Permit: Collection of surface samples: High- and low-touch surface samples were collected using dry surface swabs (Medical Wire Dry Swabs, MW730, Corsham, UK) as described previously 19,20.
    Sex as a biological variablenot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Cell Line Authenticationnot detected.

    Table 2: Resources

    Experimental Models: Cell Lines
    SentencesResources
    NIOSH BC 251, kindly provided to us by William G.
    NIOSH BC 251
    suggested: None
    Culturing was performed on Vero cells, clone 118 at 37°C, and 5% CO2 and was completed after 7 days.
    Vero
    suggested: None
    Software and Algorithms
    SentencesResources
    An airflow of 12.5 L/min through the BioSampler was established by connecting the outlet of the sampler to an inhouse designed pump unit.
    BioSampler
    suggested: None
    cDNA was synthesized using LunaScript® RT SuperMix Kit (New Engeland Biolabs, USA) and library preparation was performed using EasySeqTM RC-PCR SARS-CoV-2 Whole Genome Sequencing kit (Nimagen, The Netherlands) according to manufacturer’s instructions.
    New Engeland Biolabs
    suggested: None
    Genomes with >90% genome coverage were uploaded to GISAID (https://www.gisaid.org/)40, with accession IDs EPI_ISL_3047866, EPI_ISL_3047867, EPI_ISL_2259188, EPI_ISL_2259136 and EPI_ISL_2259122 and phylogenetic and analysis performed using MAFFT alignment software (Galaxy Version 7.221.3,
    MAFFT
    suggested: (MAFFT, RRID:SCR_011811)
    Galaxy
    suggested: (Galaxy, RRID:SCR_006281)
    FFT-NS method) 41 and phylogenomic software IQ-TREE 2.1.3 (Galaxy Version 1.5.5.3)42–44, using ModelFinder (with best predicted method GTR+F+I), ultrafast bootstrapping (1000 replicates) and maximum likelihood tree reconstruction.
    IQ-TREE
    suggested: (IQ-TREE, RRID:SCR_017254)

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: An explicit section about the limitations of the techniques employed in this study was not found. We encourage authors to address study limitations.

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    Results from scite Reference Check: We found no unreliable references.

    About SciScore

    SciScore is an automated tool that is designed to assist expert reviewers by finding and presenting formulaic information scattered throughout a paper in a standard, easy to digest format. SciScore checks for the presence and correctness of RRIDs (research resource identifiers), and for rigor criteria such as sex and investigator blinding. For details on the theoretical underpinning of rigor criteria and the tools shown here, including references cited, please follow this link.

  3. Version published to 10.1101/2022.02.16.22271053v1 on medRxiv